QDir::isAbsolutePath(name) thinks any path starting with a slash is
absolute; however, to return a valid absolute path, we need to put a
drive prefix onto such a name. So use QFileSystemEntry::isAbsolute()
for that check (it believes in the need for a drive, or UNC prefix)
and handle the absolute-but-for-drive case when it arises.
Add a regression test and make related changes to existing tests.
Task-number: QTBUG-50839
Change-Id: Id5d2b2586bb1423fa2d9375a298a4bb5241cffe0
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
54190595ef